Among the most critical and challenging medical problems in the emergency medical, and particularly the aeromedical field, is the detection and discrimination of heart and breathing sounds of seriously injured patients in environments having high levels of background noise. During the initial stages of diagnosis and/or treatment, the physician needs to stabilize or maintain each patient's condition. Effective stabilization cannot be accomplished without monitoring the heart and respiration of the patient. Specifically, the patient may be susceptible to shock, which can be detected by monitoring vital signs, including heart rate, respiration and blood pressure. In addition, if the patient has experienced chest trauma, the detection and monitoring of respiration is critical for treating possible lung collapse or conditions causing the lungs to fill with fluid. When this occurs and the patient is intubated effective tube placement and integrity needs to be monitored.
Severely injured patients are often evacuated by helicopter to a remote location for proper treatment. For example, patients injured in the field during combat are often evacuated to a remote treating area by a Blackhawk UH-60 helicopter. Traditional auscultation devices have proved ineffective in accurately monitoring a patient's heart and breathing sounds when high levels of background noise, such as those created by helicopters, are present. Background noise can comprise airborne acoustic waves as well as structure borne sounds and vibrations which couple to the patient's body. The noise level generated by a Blackhawk UH-60 helicopter, for example, can exceed 100 dBA. Conventional acoustic and electronic stethoscopes cannot reliably detect heart sounds or respiration under these conditions, making it impossible to discriminate subtle features in either physiological signal.
The background noise can include discrete frequencies, broadband noise and/or a combination of both. All of these components may be present in varying degrees in high-noise environments such as battlefields and civilian emergency medical services (EMS) sites. Noise can interfere with the physiological sounds a user wishes to hear through a stethoscope because there are several leakage pathways including, through and around the earpieces, through the acoustic tube connecting the earpieces with the stethoscope head (via mechanical coupling), between the stethoscope head and the patient's body, and through the patient's body directly into the stethoscope head via mechanical coupling between a vibrating transport vehicle and the patient's body.
Although passive acoustic stethoscopes can be functional in environments having a background noise of up to about 80 dBA, medical professionals often need to ascertain physiological patient information in environments having higher levels of background noise.
Accordingly, a need remains for a stethoscope having both an acoustic amplifying system and an active Doppler physiological activity detection system that is effective in high background noise environments and overcomes the limitations, disadvantages, or shortcomings of known auscultation devices.
The high acoustic background noise of military and civilian helicopters and other medical transport vehicles require that ear protection be used by treating physicians. Hence the stethoscope earpieces must be integrated in some manner with the ear protection. For example, in the Army, Communication Ear Plugs (CEPs) placed directly into the external ear canal are used to reduce noise leakage from the surrounding air into the ears while directing communication signals into miniature speakers in-situ in the plug. Replacement of the conventional acoustic tube (hollow pipe) of a normal stethoscope with wires in an electronic stethoscope (which has a transducer in place of the bell and diaphragm) provides an electrical connection that eliminates the noise transmitted through the walls of the tube. However, this has no effect on noise leakage pathways at the transducer where the signal is received. Prior art devices using a microphone inside an air-coupled sensor head do not reduce the noise leakage between the head of the stethoscope and the patient's body as both the noise and the signal are amplified.
Accordingly, a need remains for a stethoscope that incorporates the capability to enhance the auscultation of physiological sounds while rejecting ambient noise.